Hydrofluoric acid gas was allegedly discharged into the surrounding environment from the Samsung Electronic Co. semiconductor line in Hwaseong City after a fatal leakage from one of the pipelines last month, according to a police investigation Friday.

The latest development runs counter to the earlier statement by the world’s largest semiconductor maker that no toxic chemical was leaked outside the factory.

“After analyzing CCTV footage in the central chemical supply system of the factory, the police learned that the toxic gas seemed to have leaked outside the factory line,” said an official from the Gyeonggi Provincial Police Agency.

In the video footage, four maintenance workers in yellow protective clothing were seen discharging the hydrofluoric acid gas from inside the Central Chemical Supply System of the chip plant using large electronic fans at around 6 to 7 a.m. according to the official. 

Fumes were also seen on the footage.

The police are investigating whether the discharge was illegal as Article 31 in the Clean Air Conservation Act states that toxic chemicals can be released outside without being treated in emergencies to prevent explosion and fire.

Samsung denied the allegation. 

An official from Samsung Electronics said the fans were turned on to discharge neutralized vapors of the leaked hydrofluoric acid gas after firefighters had treated it.

"We are currently investigating on what has caused the fumes to appear on the CCTV, and its components," the company said in a statement. 

Some 2 to 10 liters of a 50 percent solution of hydrofluoric acid leaked on Jan. 27, killing one maintenance worker and injuring four others.

Samsung had said in a statement released following the incident that there was no possibility of the fatal gas being leaked further and that the situation was contained.

The Environment Ministry and the Gyeonggi provincial government launched a special probe into the incident to decide whether the company properly managed the substances.

“The ministry asked the police for the entire video footage and more evidence to verify if the workers let the toxic chemical outside,” said a ministry official from the air pollution control division.

“We will then decide whether the workers purposely discharged the gas without being treated.”

Samsung and its contracted firm STI Service in charge of dealing with chemicals at the plant had come under fire for their clumsy response and a belated report to the authorities of the incident.

The plant is located less than 4 kilometers from Dongtan New Town in Hwaseong City and Suwon City, where 1.3 million residents live in both areas.

Following the new development, the Environment Ministry may also take some flak for conducting a flawed investigation.

The ministry conducted its own investigation on Jan. 28, around 18 hours after the incident, to look for toxic residue around the plant. It had detected that no trace of the chemical were detected.

The ministry’s investigation inside the factory line, however, detected 8 parts per million of hydrofluoric acid at a place near the broken pipeline valve, but no chemical outside the plant, an official from the ministry’s chemicals management division told The Korea Herald. The official said there were no immediate plans for further probe to measure any potential damages.

By Kim Young-won  (wone0102@heraldcorp.com)